Process control systems, such as distributed or scalable process control systems like those used in chemical, petroleum or other processes, typically include one or more process controllers communicatively coupled to at least one host or user workstation and to one or more field devices via analog, digital or combined analog/digital buses. The field devices, which may include, for example, control valves, valve positioners, switches and transmitters (e.g., temperature, pressure and flow rate sensors), perform functions within the process such as opening or closing valves and measuring process parameters. The process controller receives signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, and uses this information to implement a control routine to generate control signals, which are sent over the buses to the field devices to control the operation of the process. Information from each of the field devices and the controller is typically made available to one or more applications executed by the user workstation to enable an operator to perform any desired function regarding the process, such as viewing the current state of the process, modifying the operation of the process, etc. In the event that a field device fails, the operational state of the entire process control system can be jeopardized.
Field devices in a process plant include, in some instances, pressure regulators. The pressure regulators may be used by themselves to regulate the pressure of a gas, or may be used in combination with a pneumatically powered actuator actuating a valve. Electronic pressure regulators may be controlled by external programmable logic controllers or by on-board programming.